1. Field of the Invention
The present invention relates to a vehicle seat with an integral seat belt mechanism.
2. Description of the Related Art
FIG. 8 shows a conventional vehicle seat A and a conventional individual seat belt mechanism B. The seat belt mechanism B has a seat belt C, a retractor D disposed in a vehicle door pillar, a tip anchor E engaged with a tip end of the seat belt C, a tongue plate F attached at the midpoint of the seat belt C and a tongue anchor G with which the tongue plate F is detachably engaged.
In the individual seat belt mechanism, the retractor D, the tip anchor E and the tongue anchor G are fixed or connected to a vehicle body. Accordingly, when the seat belt C supports the driver or passenger against shock caused by an accident and the like, impact load acting on the seat belt C is directly transmitted to the vehicle body. In other words, the impact load acting on the seat belt C is not transmitted to the vehicle seat A.
The above seat belt mechanism is very excellent in supporting the driver or passenger. However, vehicle manufacturing line requires the operation of assembling the vehicle seat and the seat belt mechanism individually to the vehicle body. Moreover, the seat belt mechanism has a disadvantage in comfort. Even if the position of the vehicle seat A is adjusted, the position of the seat belt mechanism B is not adjusted.
JP 2002-59770A discloses a vehicle seat with an integral seat belt mechanism. The integral seat belt mechanism has a retractor (43) fixed to a seat back frame (20), a tip anchor (41) that is fixed to a seat bottom frame (11) and coupled to a tip end of a seat belt and a tongue anchor (44) that is fixed to the seat bottom frame (11) and detachably engaged with a tongue plate (42).
In the integral seat belt mechanism, even if the position of the vehicle seat is adjusted backward or forward, the relative position of the seat belt with respect to the vehicle seat is not changed. For this reason, the integral seat belt mechanism offers an excellent comfort. Further, since the integral seat belt mechanism is previously attached to the vehicle seat, the number of processes in the vehicle manufacturing line can be reduced. However, impact load acting on the integral seat belt mechanism is entirely transmitted to the vehicle seat. Accordingly, when the seat belt mechanism is attached to the vehicle seat, the strength of the framework of the vehicle seat needs to be improved.
For example, JP 2002-59770A discloses reinforcing plates (21), (22) for preventing the seat back frame (20) from deforming due to load applied through the seat belt. JP 11-278127A discloses a damper (14) for preventing a seat back frame (3) from falling frontward due to impact load. However, the above-mentioned conventional arts do not comprise a height control mechanism of the vehicle seat.
US 2001/0005003A1 discloses a tip anchor (72) attached to a height adjustable seat bottom frame (11) with a shaft (75). Further, FR 2796602A discloses a tongue anchor (32) attached to a height adjustable seat bottom frame (11) with a shaft (246). Although these two prior arts has a mechanism for adjusting the height of the vehicle sheet, only the tip anchor or the tongue anchor of the seat belt mechanism is attached to the vehicle seat. The reason will be described below.
When the tip anchor or the tongue anchor is attached to the height adjustable seat bottom frame, impact load applied to the seat belt acts on the seat bottom frame as a force of moving the seat bottom frame upwards. The conventional and typical height control mechanism has a high resistance to down force, but has a low resistance to upper force. For this reason, the above-mentioned two prior arts have a height lock mechanism for preventing the seat bottom frame from moving upward due to the impact load.
When only the tip anchor or the tongue anchor is attached to the vehicle seat, only a part of the impact load applied to the seat belt is transmitted to the vehicle seat and remaining impact load is dispersed over the vehicle body. Consequently, the height lock mechanism can be manufactured so as to have a practical size. However, since all impact load is transmitted to the vehicle seat in the integrated seat belt mechanism, the height lock mechanism becomes heavy. Such heavy height lock mechanism cannot satisfy automobile manufacturers.